Pyrometallurgical reduction of manganese-rich black mass from discarded batteries using charcoal

Abstract

The recycling of heavy metals contained in alkaline batteries allows minimizing the environmental impact and gives an alternative use to this waste, which can be used in the pyrometallurgical industry. In the present research work, we evaluated the possibility of reducing the manganese oxide black mass from discarded alkaline batteries to produce metallic manganese, using charcoal as a reducing agent. The procedure begins with the characterization of the raw materials, the stoichiometric calculations and the preparation of a practical method to produce self-reducing pellets, composed of manganiferous material, charcoal and bentonite as agglomerant. Computer simulations were performed, to establish the appropriate thermodynamic conditions for reduction. The tests were carried out in a tubular-type furnace, and the results obtained were evaluated using optical microscopy, scanning electron microscopy coupled with microchemical analyses and X-ray diffraction techniques. It was verified that the agglomerates showed a self-reducing behavior, so an increase of the %Mn in the samples due to increasing the temperature of the reduction treatment was found, as well as the presence of a metallic manganese phase that was identified by X-ray diffraction analysis.Graphical Flow sheet for the production of self-reducing pellets containing eucalyptus charcoal for the recycling of manganese contained in spent alkaline batteries